Tacrolimus is a widely used immunosuppressive drug for post renal transplantation. The concentration of tacrolimus is important for success in management of renal recipients. The effect of genetic polymorphism on the concentration of tacrolimus is very interesting. Here, the author studied the SD11B1 rs846908 polymorphisms and tacrolimus concentrations by quantum chemical analysis. It can be seen that the AA + AA polymorphism results in less finalized tacrolimus concentration comparing to GG + GA polymorphism.